Three or four years ago, the only thing many Americans knew about Nicaragua was that it was somewhere in Latin America, suffered earthquakes and volcanic eruptions, and that a song had once been written about its capital, Managua. The song goes: "Managua, Nicaragua, it's a beautiful town. You buy a hacienda for a few pesos down . . ."

Managua, in fact, is not such a beautiful town, especially since most of it fell down during a 1972 earthquake that the world little noted nor long remembered. But at least Americans, and much of the rest of the world, now know where it is, following a year of revolutionary warfare that brought it to our television screens nightly as guerrilla youths struggled to overthrow the internationally reviled despot who had ruled for decades.

In the 32 months since they succeeded, we have spent nearly as much television time and printed columns trying to figure out what Nicaragua is. Depending on one's point of view, Nicaragua today is: the international symbol of a true "people's revolution," struggling against hegemonic U.S. aggression; or a totalitarian betrayal of all its citizens fought for, providing a launching pad for Cuban and Soviet aggression that ultimately will cross our own borders.

Having given Secretary of State Alexander M. Haig Jr. and other administration spokesmen ample opportunity to air their views that the latter characterization most applies, WETA tonight devotes an hour to the former view. "From the Ashes . . . Nicaragua Today," at 10 p.m. on Channel 26, is a lovingly put together documentary chronicling, in the lives of one family, the transformations that have taken place in Nicaragua since the despot left and the guerrillas took over.

Seen through the eyes of Jose Chavarria, a Managua shoemaker, his wife Clara and their four children, revolutionary Nicaragua is a country of personal dignity and equality, where even the poorest have a say in how things are run. It is a country still under the thumb of the United States, whose conservative government is trying to overthrow the revolution by hook, crook or starvation through aid cutoffs.

What the Chavarrias show us, as far as it goes, is impressive. The family sings together, works together and talks politics night and day. The Chavarrias and their neighbors are proud of their efforts to rid the country of former President Anastasio Somoza, and proud of their efforts to rebuild it from the rubble Somoza left behind.

There are problems with the approach used by the makers of this film, which was begun soon after the July 1979 revolutionary triumph of the Sandinista National Liberation Front guerrillas and completed last July. The first is that, as much as one appreciates the very normalcy of the Chavarria family--the comforting thought that a country can't be all Marxist-Leninist if kids and parents sit around talking about normal things--scenes of family beach parties, family gab-fests and song-fests gradually become boring.

The second is that, for all their normalcy, the Chavarrias in fact are not your average Managua family. Jose, the father, is leader of his neighborhood Sandinista Defense Committee block organization. His wife, Clara, is an activist in the government-organized Sandinista Women's Federation. One daughter, the film tells us, has "a high position" in the national women's organization and two of the girls are members of Sandinista youth brigades teaching peasants to read.

There are a few half-hearted attempts to acknowledge that, in addition to the very large menace posed by Nicaragua's northern neighbor, small problems persist. Peasants complain about the high cost of food, farmers about the still rich landlords, businessmen about the ideology of their rulers. Overall, the film is too treacly by half.

Still, one gets the impression that this version of Nicaragua, at least for the average Managuan, is a little closer to true life than that presented by Haig, et al., and one we should be aware of. And, interspersed among the smiling Chavarrias is first-rate footage from the revolutionary war itself, of the figures and style of the new government, and a couple of thoughtful interviews with other Nicaraguan figures. Among the best snippets are old black-and-white newsreels of earlier U.S. interventions, complete with doughboy Marines and pledges to save democracy that long ago rang hollow.